The trench refill and buried oxides are limiting factors for the total ionizing dose (TID) hardness of oxide isolated integrated circuits (ICs). High-density-plasma (HDP) oxide deposition is typically used for trench refill in deep submicron ICs. HDP provides trench refill capabilities without the long thermal cycles required to prevent enhanced etching, as it occurs for Tetraethyl Orthosilicate (TEOS). However, characterization of the TID radiation-induced voltage shifts for commercial HDP oxides has shown them to be more radiation sensitive than TEOS refill oxides used for previous device generations.
TID hardness of ICs is degraded by charge buildup in refill oxides of trench regions and buried oxides. Hughes et al, “Radiation Effects and Hardening of MOS Technology: Devices and Circuits”, IEEE Transactions on Nuclear Science, Vol. 50, No. 3, June 2003, provides an overview of radiation-induced effects and the many different approaches to their mitigation.
There is a need in the art for minimally invasive fabrication approaches for radiation hardening are needed to modify the charge trapping properties of deposited oxide films used in the semiconductor industry.